Counting circuit control for electrophotographic printers



March 1, 1955 2,703,280

COUNTING CIRCUIT CONTROL FOR ELECTROPHOTOGRAPHIC PRINTERS Filed May 17,1950 L. BfBUTTERFlELD ET AL 2 Sheets-Sheet l INVENTORS 159x 33.4502221729 Jkrz Xi jwlzel' 6b fl ATTORNEY March 1, 1955 1.. B.BUTTERFIELD ET AL 2,703,280

COUNTING CIRCUIT CONTROL FOR ELECTROPHOTOGRAPHIC PRINTERS Filed May 17,1950 2 Sheets-Sheet 2 ATT ORNEY United States Patent COUNTING CIRCUITCONTROL FOR ELECTRO- PHOTOGRAPHIC PRINTERS Louis Boydston Butterfield,Plainfield, and John Henry Sulzer, Union Beach, N. J., assignors toWestern Electric Company, Incorporated, New York, N. Y., a corporationof New York Application May 17, 1950, Serial No. 162,591

15 Claims. (Cl. 95--1.9)

Thisinvention relates to controls for printing and more particularly toelectrostatic printing and electrical controls including a countingcircuit for ejecting a microfilm and holder therefor after the microfilmhas been cyclically moved through an optical system to produce apredetermined number of electrostatical-ly printed copies from eachfilm.

The recent introduction of the use of electrophotographic printing,while presenting a great theoretical improvement over the existingprinting methods, is considerably limited in commercial applicationbecause of the complete lack of machinery or apparatus which can utilizethe best qualities of the electrophotographic process and yet competecommercially with high speed printers of the many well known types. Thepresent devices utilizing electrophotographic printing are manuallyoperated and require a large number of independent manually performedsteps in order to produce a single printed copy. In addition, theavailable equipment requires a complete reassembly of the printer inorder to print copies of more than one desired object.

Consequently, an object of this invention is to provide a high speedprinter of the electrostatic or electrophotographic type wherein theobjects to be printed are automatically fed into the printer andsubsequently ejected upon completion of a predetermined number ofprinted copies.

In accordance with this and other objects, one embodiment of theinvention comprises a reciprocating carrier which is adapted tocyclically move a microfilm and holder through a beam of light in anoptical system so as to produce variations in light intensity which aresubsequently applied to a photoconductive printing surface to generateelectrostatic images thereon. A photoelectric cell is positionedadjacent the moving holder to be energized thereby for producing pulsesof current which are totalized in a counting circuit adjusted so as toeject the moving microfilm and its holder upon completion of apredetermined number of movements of the film. Also, the photoelectriccell energizes a circuit which controls a printing surface actuatingmeans so that this surface moves only during the same intervals of timeas the moving microfilm.

A more complete understanding of the invention may be had byconsideration of the following detailed description in conjunction withthe accompanying drawings wherein Fig. l is a schematic view of anelectrophotographic printer disclosing the invention;

Fig. 2 is a circuit diagram of a counting circuit for controlling theapparatus of Fig. 1;

Fig. 3 is a plan view of a microfilm and a holder therefor in printingposition; and

Fig. 4 is a side elevational view of the microfilm and holder inprinting position.

Referring now to Fig. 1 of the drawings, a photoconductive printing roll11 is driven by an electric motor 12. The term photoconductive as usedin this application means those materials having such a change in theirelectrical characteristics in the transition from darkness to light thatan electrostatic image can be produced and maintained by said materialsduring an electrostatic printing cycle. Such materials include amorphousselenium, sulphur, germamium, lead sulphide, copper oxide, silverchloride, silver iodide, various combinations of-selenium and sulphurand pthers.

2,703,280 Patented Mar. 1,1955

A pair of receptacles 13 and 14 are rigidly secured opposite each otherand adjacent the periphery of the printing roll 11. Receptacle 13contains a color pigment which is used to print a desired color imageand receptacle 14 encloses a brush which is used to clean the surface ofthe printing roll 11 after each printing operation. A supply roll 15 ofpaper positioned adjacent a lower sector of the periphery of theprinting roll 11 feeds a continuous web of paper to the roll 11 forreceiving the desired color image to be printed.

Three spaced groups of electrostatic charging wires 16, 17 and 18 arepositioned adjacent three separate portions of the roll 11. The wires 16are used to place a uniform electrostatic field on the surface of thephotoconductive roll 11 and the wires 17 transfer the color pigmentimage from the surface of the roll 11 to the surface of the paper websupplied by the roll 15. The wire group 18 appliesan electrostatic fieldof a polarity reversed to the field produced by the wire group 16 on thephotoconductive surface of roll 11 so as to reduce the fatigue thereofor to prevent breakdown of the photoconductive characteristics. Thefatigue elimination effect of the wire group 18 is described more fullyand also is claimed in a copending application of Butterfield andClaybourne, Seriai Number 162,592, filed May 17, 1950.

An electric bulb 19 provides a source of light which is focused on amoving microfilm 20 (Figs. 3 and 4) by a lens 21. A movement of themicrofilm 20 through the focused light produces variations of intensityin the light which has passed through the film 20. These variations inlight intensity are then transmitted through a light restricting slit 22(Figs. 3 and 4), through an enlarging lens 23 and are finally reflectedonto the photoconductive surface of the roll 11 by mirrors 24 and 25.These light variations when applied to the photoconductive-surface ofthe moving roll 11 generate an electrostatic image which is proportionalto the variations in light intensity received on the uniformly chargedphotoconductive surface of the roll 11.

The rotation of the roll 11 carries the progressively formedelectrostatic images through the color pigment receptacle 13 wherein theelectrostatic charge on the roll 11 attracts and holds the colorpigments to form a color image on the surface of the roll 11 which imageis subsequently transferred to the paper web by the electrostatic fieldof the wire group 17. Following the transfer of the color image by theelectric field of the .Wire group 17, the surface of the roll 11 iscleaned in the receptacle 14, charged by an electric field produced bythe wires 18 to reduce fatigue, and finally charged by the wires 16 toproduce a uniform electrostatic field which is moved into the field ofthe light variations once again to produce another electrostatic image.The foregoingsteps of the electrostatic printing process are carried onin an endless sequence through the continuous start-stop rotation'of theprinting roll 11.

Microfilm feeding control centrally mounted. Since the film 20 isrecessed from both the upper and lower surface of the film holder 29,there is no danger of damaging the surface of the film 20 by accidentalabrasion or rubbing. Each of the holders 29 is also provided with twospaced vertical holes 41 and 42 (Figs. 3 and 4) which are positionedadjacent one edge of the holder 29.

An L-shaped carrier 43 having two vertical holes 44 and 45 (Figs. 3 and4) and a vertical central opening 46 rests on the top surface of theframe 26 and is adapted to be reciprocated thereon. An arm 47 issecuredto the left end of the carrier 43 and extends parallel to the uppersurface of the frame 26. A pin 48 is rigidly secured to the left end ofthe arm 47 and projects perpendicularly therefrornto engage withinthebifurcations of aforked end 49 on an upright arm 50. The arm 50 isreciprocated by a drive 60 which may be any one of the numerouswell-known types such as an eccentric system driven by an electricmotor.

The reciprocating drive 60 is controlled by a spring pressed contact 61which connects a source of power 62 to the electric motor of the drive60 through the conductors 63, 64 and 65. The contact 61 is secured tothe rack 28 in such a manner that this contact is held closed to supplypower to the drive 60 as long as a film holder 29 remains in the rack28. When the last film holder 29 which does not contain a film 20 isremoved from the rack 28, a spring 66 forces the contact 61 open and thereciprocating drive 60 is stopped.

The initial operation of the drive 60 is accomplished by dropping aholder 29 into the rack 28 to be held therein by the detent 30 so thatthe contact 61 is closed by the holder 29 against the action of thespring 66. The additional films 20 to be printed and their associatedholders 29 are stacked on top of the first placed holder 29. Operationof the drive 60 reciprocates the arm 50 thereby causing the carrier 43to move through an oscillatory cycle between a position beneath the rack28 and a position over an edge of the recess 27.

The operation of the drive 60 actuates the arm 50 to move the carrier 43under the rack 28 whereby an edge of the upper surface of the carrier 43moves the detent 30 out of its normal position to allow the first holder29 to drop onto the carrier 43. When the holder 29 is in place on thecarrier 43, the holes 41, 42 and opening 40 are aligned with the holes44, 45 and opening 46, respectively, in the carrier 43. Thereciprocating arm 50 then continuously moves the carrier 43 and theholder 29 with a microfilm 20 over the light slit 22 in the frame 26 toscan the microfilm 20 and make one printed copy thereof. If only oneprinted copy is desired, the holder 29 and its film 20 is then ejectedinto the recess 27. However, where more than one printed copy is to bemade, the particular holder 29 and film 20 must be reciprocated in thecarrier 43 past the light slit 22 to accomplish the desired number ofscanning operations. When, in the event that more than one copy isdesired, the carrier 43 and holder 29 return to a position beneath therack 28, the detent 30 is again engaged. However, the lowermost holder29 will not drop onto the carrier 43 at this time inasmuch as the formerholder 29 is still on the carrier 43. The above de scribed cycle ofoperation is repeated until the holder 29 being moved by the carrier 43is eiected therefrom. At this time, movement of the carrier 43 to engagethe detent 30 releases another holder 29 which falls into the space onthe carrier 43 occupied by the previous holder 29.

A switch 67 (Fig. 3), positioned on the frame 26 and in the path ofmovement of the carrier 43, is closed by a forward movement of thecarrier 43 an instant before the leading edge of the film 20 registerswith the slot 22 and remains closed until it is opened when the carrierclears or passes the switch and is maintained opened during the entirereverse movement of the carrier 43 toward the rack 28. The switch 67interconnects the electric light bulb 19 with a battery 68 throughconductors 69 and 70 so that the bulb 19 will only be illuminated duringthe forward movement of the carrier 43 when the microfilm 20 is scanned.Therefore, the films 20 are scanned to produce light variations on thephotoconductive surface of the roll 11 only during the forward movementof the holder 29 and, consequently, any scanning during the returnmovement of the carrier 43 toward the rack 28 is prevented.

A slit 80 in the frame 26 (Figs. 3 and 4) is so positioned below and inalignment with the path of travel of the aligned holes 42, 45 and thealigned holes 41, 44 that a beam of light from the bulb 19 will passthrough each hole in sequence and through the slit 80 to impinge on aphotoelectric cell 81 therebeneath. Since the bulb 19 is energized afterthe switch 67 is closed by the forward movement of the carrier 43 theonly light incident upon the slit 80 and, consequently, upon the cell 81is that which passes through aligned holes 42. 45 and aligned holes 41,44 as they pass over the slit 80 on the forward stroke of the filmholder 29. The distance between the slits 22 and 80 is the same as thatbetween the leading edge of the microfilm 20 and the leading edge of thehole 42 so that the first beam of light striking the photocell 81 willcorrespond exactly in time with the incidence of the first beam of lightwhich passes through the microfilm 20 to be reflected by the mirrors 24,25 and then impinged on the printing roll 11. The distance between thetrailing edge of the microfilm 20 and the leading edge of hole 41 is sopositioned that the cell 81 is energized simultaneously with thecompletion of the scanning of the microfilm 20.

Printing roll control The incidence of the first beam of light on thecell 81 produces a pulse of current which is transmitted to a photocellamplifier 82 by a conductor 83. The amplifier 82, when energized by thephotoelectric cell 81, produces a ground pulse which is applied by aconductor 86 to a contact 84 of a relay 85. The ground pulse transmittedfrom the amplifier 82 by the conductor 86 is also applied through anormally closed contact 87 of a relay 88 to and through a resistor 89and a battery 90 to ground. The ground pulse applied to the contact 84completes a circuit from ground through a battery 100, a resistor 101,the operating coil of the relay 85, the contact 84, and thence to groundin the amplifier 82 through the conductor 86. Completion of this circuitoperates relay 85 from the battery so that contacts 102, 103 and 104close and the contact 84 opens. Relay 88 remains unoperated throughoutthe duration of the first ground pulse since the ground on contact 84 isshunted around the operating coil of relay 88 by the closed contact 87.

The operation of relay 85, although removing the ground by openingcontact 84, closes a holding circuit comprising grounded contact 104,now closed, the operating coil of relay 85, resistor 101, and battery100. This holding circuit maintains the relay 85 operated after groundis removed from the contact 84. The closure of contact 102 providesground through a conductor 105 to an operating coil of a relay 106 andthence through a battery 187 to ground so that the relay 106 is operatedto close contact 108. The contact 108 is in series with an externalpower supply 109, shown here as a transformer, and with the motor 12 foractuating the printing roll 11. The operation of relay 106 to closecontact 108 energizes the motor 12 to rotate the roll 11 and since theoriginal ground pulse operating the relay 85 and, subsequently, therelay 106 was initiated by light passing through the aligned holes 42and 45, which holes register with slit 80 simultaneously with theleading edge of the microfilm 20 passing over the slit 22, the roll 11begins to rotate at the exact moment that the microfilm 20 moves acrossthe slit 22 to produce the first light variations for generating theelectrostatic image on the surface of the roll 11.

The closure of contact 103 connects ground through a contact 110 of therelay 88, conductor 120, contact 103, through a conductor 121 to anoperating coil of a stepping relay 122 (Fig. 2) and thence to groundedbattery 123. As long as this circuit remains closed, the relay 122 willbe held operated by the battery 123.

Referring again to the carrier 43, the continuing movement thereoftoward the recess 27 moves the holes 42 and 45 out of alignment with theslit 80 so that the cell 81 is no longer energized by light from bulb 19and, consequently, the ground pulse produced by the amplifier 82 isremoved from the conductor 86. The removal of ground from conductor 86removes the shunt around the operating coil of relay 88 through contact87, and the relay 88 is then operated by a circuit extending throughcontact 104, now closed, a conductor 124, the operating coil of relay88, resistor 89, and battery 90. Operation of relay 88 opens thecontacts 87, 110 and closes a contact 125. The opening of contact 110breaks the circuit comprising ground, contact 110, conductor 120,contact 103, conductor 121, the operating coil of a stepping relay 122(Fig. 2), and battery 123, whereby the relay 122 is released.

Operation of the relay 88 does not affect the continued energization ofthe motor 12 so the roll 11 continues to rotate in synchronism with themovement of the film carrier 43 past the slit 22 so that theprogressively formed light variations at the slit 22 are continuallyapplied to a new portion of the surface of the printing roll 11.However, as the carrier 43 and microfilm 20 reach the point at which thetrailing edge of the microfilm 20 passes the slit 22, the holes 41 and44- reach alignment with the slit 80 so that once again the cell 81 isenergized by light energy from the bulb 19.

As previously described, the cell 81 energizes the amplifier 82 toproduce a ground pulse which is applied through conductor 86 to thecontact 84. The ground pulse of conductor 86 is applied through contact125. now closed by the operation of relay 88, to theresistor 101,battery. 100and 'tlierethrougli toground to form a ground shuntaroundtheoperating coil of relay 85. Since relay 85, isthus deprivedotcnergization from the battery 100, the relay,85 releases and,consequently, opens contacts 102, 103 and 104, while closing contact 84.

Relay 88 remains operated although ground is removed trom the operatingcoil thereof by the opening of contact 104-because the contact 84 is nowclosed and the operating coil of the relay 88 is energized by thegroundpulse from amplifier 82 which is transmitted through conductor 86,contact 84, the operating coil of. relay 88, resistor 89 and finallythrough battery 90 to ground.

The opening of contact 103. opens the voperating path for energizing thestepping relay 122' of Fig. 2 to prevent relay 122 from operating whenrelay 88 releases.v

The opening of contact 102 breaks thecircuit energizing the relay 106 sothat contact 108 opens and subsequently removes the energization fromthe driving motor 12 to stop rotation of the printing roll 11. Since thealigned holes Y41 and 44' are placed adjacent the end of the microfilm20, the pulse initiatingthe removal of the driveto the printingroll 11occurs simultaneously with the end of the scanningprocess so thatrotation of the roll 11 ceases as soon as the entire film 20 has beenscanned.

A slight movement of the carrier 43 and the film 20 toward the recess 27and beyond the slit 22 moves the holes 41 and 45 out of alignment withthe slit 80 so that light from the bulb 19 no longer energizes thephotoelectric cell 81. As described hereinbefore, removal of theenergizationof'cell 81 renders the amplifier 82inoperative to produce aground pulse and the ground is subsequently removed from the conductor86 and contact 8 This removal ofground from contact 84 breaks thecircuit comprising ground, battery90, resistor 89, and conductor 124 sothat relay 88 releases and opens contact 125 While closing contacts 87and 110. As soon as the relay 88 is released, the circuit comprisingrelays 85 and 88 is conditioned for another two ground pulse cycleexactly the same as that just described. Since switch 67 is open on thereturn stroke of the carrier 43, the light bulb 19 will not be energizedand the holes 41, 42, 44 and 45 passing over the slit 80 fail,therefore, to produce any energization of the cell 81.

Counting circuit and ejector The pulses applied by the relays 85 and 88to the conductor 121 energize the stepping relay 122 (Fig. 2) toinitiate a counting circuit which controls the number of printed copiesto be made of a particular microfilm 20.

The stepping relay 122 (Fig. 2), which is energized by the operation ofthe relay 85 and released. by the operation of the relay 88, advancestwo pairs of contact making arms 126, 127 and 128, 129 which are rigidlysecured to a single shaft to move simultaneously and close an off-normalswitch 130. The switch 130 is arranged so that the initial movement ofthe arms 126, 127, 128, 129 closes the switch 130 and the return of thearms 126, 127, 128, 129 to a normal home position opens the switch 130.Arms 126 and 127, which are electrically interconnected, complete acircuit between a conducting ring 131 and a plurality of contacts 140which are arranged in a semicircle to be progressively contacted, stepby step, upon each advance of the arm 126. The arms 128 and 129, whichare electrically interconnected, complete a circuit between a conductingring 132 and a plurality of contacts 141 which are arranged in asemi-circle to be progressively contacted by each advance of the arm128.

The contacts 140 are adapted to be connected to ground through aplurality of switches 142 which are singly connected in parallel withground through a conductor 143. The switches 142 represent the digits 19and zero in the units denominational column, the uppermost switch 142representing the digit one 1) and the lowermost switch 142 representingthe zero or cipher, and the other intervening switches 142 representingthe digits two to nine (2-9), inclusive. Anyone of the switches 142 maybe closed to connect the respectively associated contact 140 to groundin accordance with the particular digit desired to be registered in theunits denominational column. Although the contacts 140 are shown asbeing manually grounded through the switches 142, they also may begrounded by any of the grounding circuits which are controlled bypunched cards or punched tapes as disclosed in'a copendin'g applicationof Butterfield 6. and.SulZer, Serial No. 186,008 filed.September .21,'-1950, now Patent No. 2,641,997, issuedJune 16,1953.

The operation of the off-normal switch on receipt of the first pulsefrom. the relay 122 closes contacts 144 and 145, which contacts remainclosed until the relay 122 is reset to the normal home position. Contact145, when closed, connects ground to. a pair of open contacts 146 and147 of a relay 148 through a conductor149; Contact .144, whenclosed,connectsbattery 150 to the wind ing of a reset relay 161. A contact 162is: adapted to be connected to ground through..a conductor 163 and anormally closed contact 164 of a normally operated relay 165. 'lhe relay165 isoperated by an energizing circuit comprising ground, a.normallyclosedcontact 166 of a relay 167, aconductor 168, theoperating coil'ofrelay 165, and a grounded battery 169.

As hereinbefore explained, the pulsesthroughthe con ductor 121 energizethe relay 122 to progressively advance the arm 126 over the contacts.140. When the arm 1'26 advances to a contact.140 which is groundedthrough switch 142 and conductor 143, a..circuit is completed fromground through conductor.143, switch 142, arm 126, arm 127, ring 131, aconductor. 170, a contact of the relay 165, a conductor181, theoperating coil ofrelay 148, and thence through groundedbattery 182. Thiscircuit energizes the relay 148 to close contacts 146, 147, 162, 228 anda contact 183.

The closing of contact 146 by the operationv of relay 148 completes aholding circuit for the relay 148 throughv ground, switch 1.30, contact.145, conductor 149, contact 146, the operating coil of relay 148,. andgrounded battery 182. the arm 126 is moved away from the groundedcontact 140 and also prevents the relay 148 from. openingin the eventthat grounding switch 142 is inadvertently or prematurely opened.Contact 147, in closing, completesa holding circuit for the relay 165through ground, switch.

1311, contact 145, conductor-149, contact 147,.conductor 168, theoperating coil, of relay 165,.and grounded battery 169.

Contact 183, when closed, completes acircuit from ground through. aconductor 184, through the. operating coil of an ejector (Fig. 1) forejecting a film holder 29 off the carrier 43, and-finally through abattery 186 to. ground. This circuit energizes the operating. coil of.the ejector 185 so that an armature 187, thereof, moves.

downward to strikethe holder 29 which is. now posi tioned directlyunderthe armature 187 so asto. force the holder. 29 out of the carrier 43 andinto therecess 2.7. Therefore, the operationof the relay 148 by the arm126 reaching a predetermined grounded contact140 causes the ejection ofthe microfilm 20 and holder 29.

in response to a predetermined number of counted movements of the film21).

Contact 162, when closed by therelay 148, energizes the reset relay 161through a circuit comprising ground, contact 164, conductor 163, contact162,-conductor 151, operating coil of relay 161, .contact 144, switch130, and grounded battery 150. Operation of therelay 161 causes the arms126, 127, 128, 129 to return to their normal home position, i. e., theposition before receipt of any pulses, and the homing movement ofthearms 126, 127, 128, 129. causes the off-normal switch 130 to. returnto its normal home position, thus opening the contacts 144 and 145. Theopening of contact 145 breaks the holding circuit associated with relay148 thus causing the relay 148 to open contacts 146, 147, 162, 183. andto break the holding circuit of relay 165. However, since the contact166 of relay 167 remains closed, the relay 165 remains operated by theground provided through the contact 166. and the conductor 168. The

opening of contact 144 breaks the energizing circuit of the reset relay161 thereby allowing advance .ofv the arms 126, 127 128, 129 uponreceipt of future Pulses by the stepping relay 122.

The opening of the contact 183, ,by the release of relay 143 breaks theenergizing circuit of the ejector185 and the armature 187 thereofreturnsto a normal position. The opening of contacts 146, 147 and 162conditions the relay 148 for another cycle of pulse counting. In effect,therefore, the energization of the reset relay 161, upon ejection of themicrofilm 2t) and holder 29, conditions the counting circuit for anothercomplete counting cycle.

In order to count more than the ten pulses made available by thetencontacts 140, asecon'dstepping relay This circuit holds the relay148. operated after 188 representing the digits in the tens denominationcolumn is connected to be energized by completion of a circuit extendingfrom ground through conducting ring 132, arms 128 and 129, contact 141,conductor 189, the operating coil of relay 188, a battery 190, andthence to ground. Relay 188 is similar to relay 122 in having two pairsof electrically interconnected arms 200, 201 and 202, 203 which aremounted for simultaneous rotation. An off-normal switch 204 is arranged,as in relay 122, to close two contacts 205, 206 upon receipt of thefirst pulse to be counted and to open the contacts 205, 206 upon returnof the arms 200, 201, 202, 203 to their normal home position.

The arm 200 completes a circuit from a plurality of contacts 207,through the electrically interconnected arms 200 and 201, to and througha ring 208 which is connected to the operating coil of the relay 165 bya conductor 209 and the conductor 168. The contacts 207 are arranged tobe selectively grounded by a plurality of switches 210 which areconnected in parallel to ground by a conductor 220. The switch 210 maybe replaced by automatic electrical grounding circuits controlled bypunched cards or punched tapes which are shown and described in thecopending application of Butterfield and Sulzer referred to inconjunction with the previous descri tion of the groundin of thecontacts 140.

Each of the contacts 207 is also connected through one of a plurality ofparallellv connected resistors 221, to and through a conductor 222. tothe operating coil of the relay 167, and therethrough to ground throu ha battery 223. The value of the resistors 221 is set high enough thatthe marginal relay 165 cannot be operated by a current from groundpassing through two resistors 221 in series and thence throu h the arms200 and 201 to the operating coil of the relay 165. This selection ofthe value of ma nitude for the resistors 221 prevents a prematureoperation of the relay 165 when the arm 200 advances to a contact 207which is not directly grounded by its associated switch 210 but which isgrounded throu h two seriallv con ected esistors 221 and a closed swi h210 associated with a different contact 207.

The arm 202 completes a circuit from a plurality of e ectricallyinterconnected cont cts 224 through the arms 202. 203 and a contact ring225 to a reset relay 227. The electricallv interconnected contacts 224are adapted to be connected to a contact 228 of the relay 148 thr ugh aconductor 229.

The closure of contact 205 by the o eration of ottnormal switch 20connects a battery 2 from ground throu h c ntact 205 to the reset relay227. The simultaneous closing of contact 206 connects conductor 189 toan operating coil of a relav 240 through a conductor 241 and hence to aground through a battery 242. A contact 243 of the relay 240, whenoperated connects ground throu h an o erating coil of a relay 244 to andthrou h a ba ery 245 to ground. A contact 246 of the relay 244. whenoperated, connects ground to winding of reset relay 161.

Referrin now to the switches 210. the top switch 210 re resents he di itone (1) in the tens denominational column while the lowermost switch 210represents zero in the tens c lumn. The intervening switches 210 reresent the di its 2 t 9, inclusive, in the tens denominational column.When any one of the switches 210 is closed. a circuit is completed fromground. throu h conductor 220. switch 210. resis r 221. conductor 222.the operatin coil f the relay 167, ba tery 223. and back to round. Thiscircuit ener izes the onerating coil of the relav 167 to open contact166. The open ng of contact 166 breaks the circuit comprisin ground,contact 166. c nductor 168. the operatin coil of relay 165. batterv 169.and ground, so that relay 165. normally oper d. releases and in doing soopens contacts 164 and 180.

Therefore. even though one of the switches 142 i closed. the relav 148cannot be operated from ground through the c nt ct 180. now open. andhence the arms 126 and 128 index to the tenth contacts 140 and 14 1.resnectivelv. As arm 128 advances to the tenth con act 141.. a circuitis com leted from ground throu h ring 132, arms 129 and 128. contact141. conductor 189. the operating coil of the relay 188. battery 190,and back to ground. whereby the relay 188 is operated to advance thearms 200, 201, and 202, 203 from the normal home position to the firstcontacts 207 and 224, respectively.

The movement of the arms 200, 201, 202, 203 also operates the off-normalswitch 204 to close contacts 205 and 206. With contact 206 closed, acircuit is established from ground through the ring 132, through arm129, arm 128, contact 141, conductor 189, contact 206, conductor 241,the operating coil of relay 240, battery 242 and back to ground, wherebythe relay 240 is operated to close contact 243. Contact 243, closed,completes a circuit from ground through contact 243, through theoperating coil of relay 244, and then through the battery 245 to groundso that relay 244 is operated to close contact 246.

Contact 246, in closing, connects ground to the reset relay 161 throughconductor 247 so that the relay 161 is energized by the battery throughthe closed contact 144 of the oif-normal switch 130. Energization of thereset relay 161 returns the arms 126, 127, 128, 129 to their normal homeposition and conditions the relays 122, 148, and for another cycle ofpulse counting as hereinbefore described. The return of the arms 128,129 to the normal home position removes the ground from the conductor189 so that relays 240 and 244 release to condition the stepping relay188 for receiving another pulse through ground from contact 141.

The process of counting ten pulses to advance the arms 200, 201, 202,203 to another contact 207 is repeated as described above until suchtime as the arm 200 advances to a contact 207 which is grounded throughthe switch 210 and conductor 220. As arm 200 engages a grounded contact207, ground is applied through conductor 220, switch 210, contact 207,arms 200, 201, ring 208, conductors 209 and 168, the operating coil ofrelay 165, and finally through battery 169 to ground so as to operaterelay 165. The operation of relay 165 to close contacts 164 andconditions relay 148 for operation the next time the arm 126 advances toa grounded contact 140 and also indicates that the counting has beencompleted in the tens denominational column.

As described above in conjunction with the resetting of the countingrelay 122 in the unit denominational column by completion of the firstcount in the tens denominational column the relays 240 and 244 connectground to the reset relay 161 to return the arms 126, 127, 128, 129 tonormal home position and to open the off-normal switch 130. The relay122 then advances the arms 126, 127, 128, 129 until arm 126 touches agrounded units contact 140 so that the relay 148 is energized by acircuit comprising grounded battery 182, operating coil of relay 148,conductor 181, contact 180, conductor 170, ring 131, arms 126 and 127contact 140, switch 142, con ductor 143, and back to ground. Operationof relay 148 closes the contacts 146, 147, 162, 183 and 228 associatedtherewith.

The closing of contacts 146, 147, 162 and 183 again performs the samefunction as described hereinbefore in conjunction with the explanationof the operation of the relays 122, 148, 161 and 165 when only a unitdenominational number of pulses are counted. The closing of contact 228completes a circuit for energizing the reset relay 227 from ground,through contact 164, conductor 163, contacts 162 and 228, conductor 229,contact 224, arms 202 and 203, ring 225, the operating coil of relay227, contact 205, and grounded battery 230. Operation of the reset relay227 moves the arms 200, 201, 202, 203 to the normal home position andreleases the off-normal switch 204. The opening of contacts 205 and 206by the release of switch 204 completes the conditioning of the entire 0unting system for the receipt of a new series of ground pulses on theconductor 121 from the relays 85 and 88.

In the special situation where the number to be counted, as determinedby the settings of the switches 142 and 210, is an even tens digit; i.e., 20, 30, the reset relay 227 is energized through the contact 162rather than through the contact 246 since the combined operating time ofrelays 148 and 165 is much less than the combined time of operation ofthe relays 240 and 244. It is apparent that the range of the countingcircuit can be extended into higher denominational columns by theaddition of any desired number of groups of stepping relays similar tothose shown and described in this particular embodiment.

General operation of the system In view of the foregoing detaileddescription, it is 9; believed that the operation of the printing andfeeding apparatus will now be understood. The. number of copies of themicrofilm 20 desired to be printed is controlled manually by an operatoror attendant setting the switches 142 and 210 so as to ground particularcontacts 140 and 207. For example. if it is desired to print 21 copiesof a particular microfilm 20 the digit 1 contact 140. inthe unitsdenominational column is. grounded by the operator closing-theswitch142. and the digit 2 contact 207 in the tens denominational columnisgrounded. by the operator closing switch 210. When switch 210. isclosed, the relay 167 is operated from ground through resistor. 221,conductor. 222,v the operating coil ofrelay 16.7, andthence throughbattery 223. to ground so;that contact 166 opens to remove ground fromthe operating coil of the relay 165.- Removal of ground from theoperating coil of relay 165 releases contacts 164 and180 thereof andindicates to the counting circuit that there is a digit entered in thetens denominational column to be countedby the relay 188. beforetherelay 165. is operated again.

The microfilm 20, whichis. desired to be printed, and its holder 29. areplaced in the rack 28. Any. additional microfilms 20. to be printed areplaced in individual holders 29 which are stacked intherack 28 on top ofthe firstiplacedholder 29; An empty holder 29 is then placed on top ofthe stack in.therack.28 to. hold the switch 61. closed. while the. lastfilm 20 is being printed.

Thefirst placed holder 29 at the bottom of the rack 28 closesthe switch61 to. complete the power supply circuitrto the motor for thereciprocating'drive 60 whereby the carrier 43, now empty, moves.towardtherack 28. Whendirectly beneath therack 28,.the carrier43.strikes the detent 30. to. release the first. microfilm holder 29,which drops in proper position on the carrier 43. The reciprocatingdrive: 6.0,,having. reached the reverse end of itscycleofmovement,nowmoves the carrier 43 toward the recess 27 andthereby.permits thedetent 3.0 to return to normal position and to engage the.next holder- 29. inthe rack 28. whereby the switch61.15;.(1'1311'11311161 closed tov supply energy to. themotor. of.thedrive 60. As the carrier 43 moves toward. the recess 27, the switch67 is closed to energize the, light bulb, 19 fromthe battery 68so, thatwhenthe holes 4,2..and 45. move into simultaneous alignment with theslit 80 andrthe leading edge of the microfilm 20 is. in alignment withthe slit 22, a beam of light passesthrough the. microfilm 20. and holes42 and 45'for energizing boththe photoconductive surface of printingroll 11 andthe control circuits.

The light energy from the bulb 19 istvaried in inten-. sity in passingthrough the microfilm 20. andis. subsequently magnified. by the lens.23, and refiected onto the photoconductive surface of the roll 11 by themirrors 24 and 25. These light variations generate an electrostaticimage on the surfaceof .the roll 11. Simultaneously with the applicationof the light variation to, the roll 11, a beam of, light passing throughthe slit 80 energizes. the photoelectric cell 81to trigger the amplifier82 to. produce a ground pulse on theconductor 8.6. Thisjground on theconductor 86 isapplied through the contact 84. to energize the relay 85,which, in operating, closes its associated contacts.102, 103.and 104.The contact 102, in closing, operatestherelay 106 to close the contact108, which then energizes the printing ro l motor 12 from the energysource 109. Therefore, the printing rollll is. rotated by the motor 12.at the same instant with respect to time as the original instant. ofincidence of the light variations ,on the roll 11.

Contact 103, when closed, applies a ground to the relay 122 through theconductor 121 so that the relay 122, is operated from battery to.advance the arms..1 26, 127, 1 28, l29fand'to close the off-normalswitch 130. The relay 148 is not operated at this time, although the arm126 is advanced one step. to touch the first contact 140- which has beengrounded. by the switch 142, because. the relay 165 has been previouslyreleased by the, operation of relay 167.

The continuing movement of the carrier 43 advances the holes 42 and 45out of alignment with the slit 80 thereby shuttingofi the beam of lightand. the cell 81 is thus deprived of energization so. that the ground isremoved from the conductor 86. by the amplifier 82. The removal ofground'from the conductor86 operates relay 88 to close'contact12S"and.to opencontacts 87 and 110; Opening contact 110 breaks theground circuit throughthe conductor 121 to the relay 122 so that relay122. returns to an unoperated state in condition for receipt of the nextpulse. In addition, the continuing forward movement of the carrier43advances new portions of the microfilm 20 past the slit 22 so that lightvariations representative of the entire area of the film 20 areprogrelsslnllely applied to the photoconductive surface of the rol Whenthe carrier 43 is advanced so that the trailing edge of the microfilm 20arrives at the slit 22, the holes 41 and 44 are aligned with the slit 80to allow a beam of lightfrorn thebulb 19 to energize the cell 81. Theenergization of cell 81 once again connects ground to the conductor 86so that relay 85 is released by virtue of the ground shunt around itsoperating coil completed through contact 125, now closed. The release ofrelay 85 opens contacts 102, 103 and'104, whereby contact 102 opens theenergizing circuit of the relay 106 and subsequently disconnects powerfrom the motor 12 through the opening of the contact 108 controlled bythe relay 106. In this manner, the printing roll 11 stops rotating atthe same instant that the trailing edge of the microfilm 20 passes overthe slit 22.

As the carrier 43 moves on toward the end of the forward cycle, theholes 41 and 44 move out of alignment with the slit 80 and the cell 81is no longer energized so that once again the ground is removed from theconductor 86 and the relay 88 is released. in releasing,.relay 88completes the conditioning of the relays 85and 88 for receipt of thenext ground pulse on conductor 86.

When the carrier 43 clears switch 67 the light bulb 19 is extinguished.Upon reaching the end of the forward cycle, the carrier43 reversesdirection to move toward the rack .28 but, asthere is no source of lightto energize the photoconductive surface of the roll 11 or the cell 81,there will be no image on the roll and no control pulses in theamplifier 82. The carrier 43 then moves into position-beneath the rack28 once again and moves the detent 30 to release the next holder 29.However, the original holder 29 is still in position on the carrier 43and the holder 29 in the rack 28 remains therein. As carrier 43 reachesthe end of the reverse cycle of movement, the drive 60 moves the carrier43 in a forward direction toward the recess 27 and in doing so thedetent 30 closes to securethebottom holder 29 in position on the rack28.

The above described cycle of operation is repeated eight more timesuntil on the tenth forward movement ofthe carrier 43, the relay 122 isenergized to advance thearm-128 to engage the tenth contact 141 wherebya circuit is completed from ground through ring 132, arms 129 and 128,contact 141, conductor 189, the operating coil. of-relay; 188, andgrounded battery 190. Completion of this circuit operates relay 188 toadvance the arms 200,- 201, 202, 203 oneposition from the normal homeposition and also to close the off-normal switch 294. The operation ofswitch 204 closes contact 206 to initiate successive operation oftherelays 240 and 244 for connecting ground to the reset relay 161. Thereset relay 161, when energized, returns the arms 126, 127, 128, 129 tonormal home position and releases the oil-normal switch 130, whereby therelay 122 is conditioned to receive a; new cycle of ten pulses.

Onceagain the relays 85-and 88 operate in response to ten additionalforward or scanning movements of the carrier 43 so that the arm 128is'again moved to engage the tenth contact'141 and completes anenergization circuit forfthe relay 183. When relay 188 receives thissecond pulse, representing the twentieth forward or scanning movementofthe carrier 43, the arm 200 is advanced to engage the; grounded digit 2contact 297 so as to complete a. circuit from'ground through conductor220, switch 210,- contact 207, arms 20%! and 201, ring 208, conductors209 and 168, the operating coil of relay 165, and grounded battery 169.This circuit operates relay 165 to close: the contacts 180, 164 andindicates that the tens denominational column requirement (20 counts)has been fulfilled so that the next time the arm 126 engagesthe'grounded contact the ground will be applied to the operating coil ofrelay 148. The reset relay 161 is again energized by the relays 240, 244to reset the arms 126, 127, 128, 129 to the normal home position andalso ot open the off-normal switch 130.

As. the carrier. 43 makes'the next forward movement; i. e., thetwenty-first, the arm 126 is advanced by relay 122 to touch the groundedfirst contact 140 and thereby completes the energizing circuit of relay148 comprising ground, conductor 143, switch 142, contact 140, arms 126and 127, ring 131, conductor 170, contact 180, conductor 181, theoperating coil of the relay 148, and grounded battery 182. The operationof relay 148, closes contacts 146, 147, 162, 183 and 228. The closing ofcontact 162 completes a circuit from ground to operate the relay 161,which, when operated, returns the arms 126, 127, 128, 129 to normal homeposition and also opens the off-normal switch 130. The closing ofcontact 228 completes a circuit from ground through the operating coilto operate the relay 227, which, when operated, returns the arms 200,201, 202, 203 to the normal home position and also opens the off-normalswitch 204. With both relays 122 and 188 reset, the counting circuit isconditioned for another complete counting cycle in accordance with thepermutation of switches 142 and 210 that are to be closed by theoperator to control the next desired number of copies to be printed.

The contact 183, when closed, completes a circuit from ground throughcontact 183, conductor 184, ejector 185, battery 186, and thence toground whereby the ejector 185 is energized to move its armature 187downward. The ejector armature 187, in moving downward, strikes theholder 29 moved by the carrier 43 and forces the holder 29 into therecess 27 to terminate the printing cycle of the first microfilm 20.

Thereafter, the carrier 43 returns to the rack 28 to receive a secondholder 29 with a second microfilm 20 to be printed. At this time, theswitches 142 and 210 are set, either manually or by the automatic meansreferred to in conjunction with the copending application of Butterfieldand Sulzer, Serial No. 186,008, filed September 21, 1950, now Patent No.2,641,997, issued June 16, 1953, to the number of copies which it isdesired to print. The cycle of operation for the printer and feedingmeans described above is then repeated until such time as the lastholder 29 and microfilm 20 which it is desired to print have beenejected. At that time the dummy holder 29, containing no microfilm 20drops into position on the carrier 43 and in doing so releases theswitch 61 so that the spring 66 forces the switch 61 open to render thereciprocating drive 60 inoperative until another holder 29 and film 20are again placed in the rack 28 for printing.

' It is to be understood that the above-described embodiment is simplyillustrative of an application of the principles of the invention andnumerous other embodiments may be readily devised by those skilled inthe art which will embody the principles of the invention and fallwithin the spirit and scope thereof.

What is claimed is:

1. In combination, a photoconductive printing surface, means for movingsaid printing surface, means for placing an electrostatic charge on thesurface, a source of light energy, an optical system for projecting thelight energy onto said charged surface to modify the charge thereon, andmeans for varying said light energy in synchronism with the movement ofthe printing surface, said light varying means comprising a plurality ofholders for carrying objects to be printed, said holders each having twolight transmitting portions therein, means for repetitively moving oneof the holders through the light energy to produce variations therein inaccordance with the object carried by the moving holder, light sensitivemeans, means for energizing the light sensitive means in response to themovement of the two light transmitting portions through the light energyto produce a first and a second electrical pulse, said first pulseproducing a counting pulse and actuating the printing surface movmgmeans, said second pulse de-actuating the printing surface moving means,a counting circuit energized by said counting pulse for totalizing aseries of such countmg pulses, and means energized by said countingcircuit upon rece pt of a predetermined number of pulses for e ectingsaid moving holder whereby another of the pluralrty of holders may bemoved into printing position.

2. In combination, a photoconductive printing surface, means for movingsaid printing surface, means for placing an electrostatic charge on thesurface, a source of llght y. an optical system for projecting the lightenergy onto said charged surface to modify the charge thereon, and meansfor repetitively providing variations in said light energy insynchronism with the movements of the surface, said means comprisnig aplurality of holders for carrying objects to be printed, said holderseach having two light transmitting portions therein, means forrepetitively moving one of the holders through the light energy toproduce light variations therein in accordance with the object carriedby the moving holder, light sensitive means, means for energizing thelight sensitive means in response to the movement of the two lighttransmitting portions through the light energy to produce a first andsecond electrical pulse, said first pulse producing a counting pulse andenergizing the printing surface moving means, said second pulsede-energizing said printing surface moving means, a circuit connected tosaid light sensitive means for totalizing the counting pulses, meansconnected to said counting circuit for resetting said counting circuitto a zero pulse count after said circuit counts a predetermined numberof pulses, and means acting simultaneously with said resetting means forreplacing said moving holder with another of the plurality of holderswhereby a second of the plurality of objects is produced as anelectrostatic image on the printing surface.

3. An electrophotographic printer for reproducing an object comprisingphotoconductive printing means, means for applying an uniformelectrostatic charge to said printing means, a light source, cyclicallymoving means for moving the object past said light source, an opticalsystem for applying said light source as varied by the obiect movingtherepast to said printing means to produce a light image thereon,photoelectric means responsive to light from said light source duringeach cyclic movement of the object moving past said light source, andejecting means controlled by said photoelectric means responsive to thelight for ejecting the object upon completion of a predetermined numberof cycles of movement of the object.

4. An electrophotographic printer for reproducing an object comprisingphotoconductive printing means. means for moving said printing means,means for applying an uniform electrostatic charge to said printingmeans. a li ht source, cyclically moving means for moving the objectpast said light source. an optical system for applying said li ht sourceas varied by the obiect moving therepast to said printing means toproduce a light image thereon, photoelectric means responsive to li htfrom said light source during each cyclic movement of the obiec't movingpast said light source, ejecting means controlled by said photoelectricmeans res onsive to the light for ejecting the obiect upon completion ofa predetermined number of cycles of m vement of the obiect, and meanscontrolled by said photoelectric means for controlling movement of saidprinting means moving means. whereby said printing means will be movedonly during the movement of the obiect past said light source.

5. An electrophotographic printer for reproducing an obiect comprisingphotoconductive printing means, means for applying an uniformelectrostatic char e to said printing means, a li ht source. c clicallymoving means for moving the object past said light source. an opticalsystem for applying said light source as varied by the object movingtherepast to said printing means to produce a light image thereon,photoelectric means responsive to li ht from said light source duringeach cyclic movement of the object moving past said li ht source,counting means controlled by said photoelectric means responsive to theli ht for counting the number of cycles of movement of the obiect, and eecting means controlled bv said counting means for eiecting the obiectafter a predetermined number of cyclic movements has been counted.

6. An electrophotographic printer for re roducing a plurality of obiectscomprising hotoconductive printing means. means for applying an uniformelectrostatic charge to said printing means, a light source, cyclicallymoving means for moving one of the objects ast said light source. an otical system for a plying said li ht source as varied by the ob ectmoving therepast to said printing means to produce a li ht imagethereon, photoelectric means respon'sive to light from said light sourceduring each cyclic movement of the object moving past said light source,and means controlled by said photoelectric means responsive to the lightfor replacing the moving object with another of the plurality of objectsafter a predetermined number of cycles of movement of the moving ob ect.

7. kn electrpphotographic printer for reproducing a plurality of ob ectscomprising photoconductive printing means, means for applying anunifionm electrostatic charge to said printing means, a light source,cyclically moving means for moving one of the objects past said lightsource, an optical system for applying said light source as varied bysaid object moving therepast to said print ng means to produce a lightimage thereon, photoelectric means responsive to light from said lightsource during each cyclic movement of the object moving past said lightsource, means controlled'by said photoelectric means responsive to thelight for replacing the moving ob ect with another of the plurality ofobjects after a predetermined number of cycles of movement of the movingob ect, and means controlled by the replacement of the last of theobjects to be reproduced for rendering said cyclically opcrating meansinoperative.

'8. An electrophotographic printer for reproduc ng a plurality ofobjects comprising PhOlIOCOIIdUCtIVB PI'IIIt'mg means, means forapplying an uniform electrostatic charge to said printing means, a lightsource, cyclically moving means for moving one of the objects past saidlight source, an optical system for applying said light source as variedby the object moving therepast to said print ng means to produce a lightimage thereon, photoelectric means responsive to light from said lightsource during each cyclic movement of the object movmgpast said lightsource, counting means controlled by said photoelectric means responsiveto the light for counting the number of cycles of movement of theobject, and means controlled by said counting means for replacing themoving ob ect with another of the plurality of objects after apredetermined number of cycles of movement of the moving ob'ect.

9. An electrophotographic printer for reproducing a plurality of objectscomprising photoconductive printing means, means, for applying anuniform electrostatic charge to said printing means, a light source,cyclically moving means for moving one of the plurality of objects pastsaid light source, said means having control indicia there- On forpassing light from said light source, an optical system for applyingsaid light source as varied by the ob ect moving therepast to saidprinting means to produce a light image thereon, photoelectric meansresponsive to the light passed by said indicia from said light source,counting means controlled by said photoelectric means for counting thenumber of cyclic movements of the object, and an ejector controlled bysaid counting means for ejecting the moving object upon completion of apredetermined number of cycles of movement of said cyclically movingmeans.

10. An electrophotographic printer for reproducing a plurality ofobjects comprising photoconductive printing means, means for applying anuniform electrostatic charge to said printing means, a light source,cyclically moving means for moving one of the objects past said lightsource, an optical system for applying said light source as varied bythe object moving therepast to said printing means to produce a lightimage thereon, photoelectric means responsive to light from said lightsource during each cyclic movement of the object moving past said lightsource, counting means controlled by said photoelectric means responsiveto the light for counting the number of cycles of movement of theobject, means under the control of said counting means for ejecting theobject from said cyclically moving means after a predetermined number ofcycles of movement, and means forming a portion of said counting meansfor varying the predetermined number of cvcles at which said ejectingmeans will be operated.

11. An electrophotographic printer for reproducing a plurality ofobjects comprising photoconductive printing means, means for applying anuniform electrostatic charge to said printing means, a light source,cyclically moving means for moving one of the objects past said lightsource, an optical system for applying said light source as varied bythe object moving therepast to said printing means to produce a lightimage thereon, photoelectric means responsive to light from said lightsource during each cyclic movement of the object moving past said lightsource, counting means controlled by said photoelectric means responsiveto the light for counting the number of cycles of movement of theobject, means connected to said counting means for selectivelypredetermining the number of cycles of movement to be counted, meanscontrolled by said counting means upon completion of the predeterminedselection to return said a 14 counting means to its initial position,and ejecting means controlled by said counting means for ejecting themoving object upon completion of the predetermined selection of numberof cycles of movement.

12. An electrophotographic printer for reproducing objects comprising aplurality of holders for carrying the objects to be reproduced,photoconductive printing means, means for applying an uniformelectrostatic charge to said printing means, a light source, cyclicallymoving means for moving one of said holders past said light source, anoptical system for applying said light source as varied by the objectmoving therepast to said printing means to produce a light imagethereon, photoelectric means responsive to light from said light sourceduring each cyclic movement of said holder moving past said lightsource, means controlled by said photoelectric means responsive to thelight for counting the number of movements of said holder, and meanscontrolled by said counting means for ejecting said moving holder uponcompletion of a predetermined number of movements of said holder.

13. An electrophotographic printer for reproducing objects comprising aplurality of holders for carrying the objects to be reproduced,photoconductive printing means, means for applying an uniformelectrostatic charge to said printing means, a light source, cyclicallymoving means for moving one of said holders past said light source, anoptical system for applying said light source as varied by the objectmoving therepast to said printing means to produce a light imagethereon, photoelectric means responsive to light from said light sourceduring each cyclic movement of said holder moving past said lightsource, means controlled by said photoelectric means responsive to thelight for counting the number of movements of said holder, and meanscontrolled by said counting means for replacing said moving holder withanother of said plurality of holders upon completion of a predeterminednumber of movements of said holder.

14. An electrophotographic printer for reproducing objects comprising aplurality of holders for carrying the objects to be reproduced,photoconductive printing means, means for applying an uniformelectrostatic charge to said printing means, a light source, cyclicallymoving means for moving one of said holders past said light source, anoptical system for applying said light source as varied by the objectmoving therepast to said printing means to produce a light imagethereon, photoelectric means responsive to light from said light sourceduring each cyclic movement of said holder moving past said lightsource, means controlled by said photoelectric means responsive to thelight for counting the number of movements of said holder, meanscontrolled by said counting means for replacing said moving holder withanother of said plurality of holders upon completion of a predeterminednumber of movements of said holder, and means controlled by saidcounting means for rendering said cyclically moving means inoperativeupon completion of a predetermined number of cycles of movement of thelast of said holders.

15. An electrophotographic printer for reproducing objects comprising aplurality of holders for carrying the objects to be reproduced,photoconductive printing means, means for applying an uniformelectrostatic charge to said printing means, a light source, cyclicallymoving means for moving one of said holders past said light source, anoptical system for applying said light source as varied by the objectmoving therepast to said printing means to produce a light imagethereon, photoelectric means responsive to light from said light sourceduring each cyclic movement of said holder moving past said lightsource, means controlled by said photoelectric means responsive to thelight for counting the number of movements of said holder, meanscontrolled by said counting means for replacing said moving holder withanother of said plurality of holders upon completion of a predeterminednumber of movements of said holder, and means forming a portion of saidcounting means for varying the predetermined number of movements atwhich said replacing means will be operated.

(Other references on following page) 15 1:6 UNITEDSTATES PATENTS 23 ,304gorelsnsen lskug. 31, 192

2, ,809 arson ept. 12, 19 $53 323 gnyder 5%; 2,406,040 Ryan et a1. Aug.20, 1946 2,221,776 f 8 1940 2,600,470 Breuers et a1. June 17, 1952 ar I5 2,609,680 Caldwell Sept. 9, 1952 2,228,820 Griffith Ian. 14, 1941

1. IN COMBINATION, A PHOTOCONDUCTIVE PRINTING SURFACE, MEANS FOR MOVINGSAID PRINTING SURFACE, MEANS FOR PLACING AN ELECTROSTATIC CHARGE ON THESURFACE, A SOURCE OF LIGHT ENERGY, AN OPTICAL SYSTEM FOR PROJECTING THELIGHT ENERGY ONTO SAID CHARGED SURFACE TO MOFIFY THE CHARGE THEREON, ANDMEANS FOR VARYING SAID LIGHT ENERGY IN SYNCHRONISM WITH THE MOVEMENT OFTHE PRINTING SURFACE, SAID LIGHT VARYING MEANS COMPRISING A PLURALITY OFHOLDERS FOR CARRYING OBJECTION TO BE PRINTED, SAID HOLDERS EACH HAVINGTWO LIGHT TRANSMITTING PORTIONS THEREIN, MEANS FOR REPETIVELY MOVING ONEOF THE HOLDERS THROUGH THE LIGHT ENERGY TO PRODUCE VARIATIONS THEREIN UNACCORDANCE WITH THE OBJECT CARRIED BY TE MOVING HOLDER, LIGHT SENSITIVEMEANS, MEANS FOR ENERGIZING THE LIGHT SENSITIVE MEANS THE RESPONSE TOTHE MOVEMENT OF THE TWO LIGHT TRANSMITTING PORTIONS THROUGH THE LIGHTENERGY TO PRODUCE A FIRST AND A SECOND ELECTRICAL PULSE, SAID FIRST PULSPRODUCTING A COUNTING PLUS AND ACTUATING THE PRINTING SURFACE, MOVINGMEANS, SAID PLUS DE-ACTUATING THE PRINTING SURFACE MOVING MEANS, ACOUNTING CIRCUIT ENERGIZED BY